1. Field of the Invention
The present invention relates to a driving device for an optical system and more particularly to a driving device which performs focusing and zooming, etc. on manufactured products in an optical inspection system.
2. Prior Art
In conventional optical systems which execute inspection of manufactured products, the functions of focusing and zooming, etc. are performed by moving movable lenses of lens group (which is made up with fixed lenses and movable lenses) so as to alter the distance between the movable lenses and fixed lenses.
In this case, electrical driving device is used which transmits the rotary force of a small motor to a feed screw mechanism via gear train so that a retaining assembly which holds the movable lenses in moved along linear guide path.
In this prior art, since a mechanism which converts the rotation of the electric motor into linear motion is required, the operating speed is somewhat limited. Thus, such a conversion mechanism is inappropriate for use in optical systems when a high-speed operation or a high-speed response is required.
In addition, since the lenses cannot be accurately positioned due to backlash in the mechanism, etc., a sharp image cannot be obtained. Moreover, when high-frequency operation is continued for a considerably long period of time, the useful life of the system is shortened.